In a chroma sensor or a turbidity sensor, an optical path needs to fuse light of two different wavelengths. In the process of fusing light in the prior art, the light transmission direction of different light sources has to be adjusted through a combination of multiple sets of prisms, in order to realize light fusion into one and the same optical path. However, such a design makes the light emitted by different light sources experience different optical path lengths before fusion, thus affecting the effect of light fusion, and this design uses relatively more prisms and/or lenses, making the optical structure complicated.
In other designs, optical fibers are used to transmit light from different light sources, for example, light from two light sources is fused and output using a Y-type optical fibre. The introduction of optical fibres solves the problem of different optical path lengths, but reduces the efficiency of light fusion. Moreover, optical fibres are fragile and expensive. In addition, since the sensor needs to be compact, the optical fibre is difficult to install and is not suitable to be used in a large amount in the sensor.
The technical problem to be solved is to overcome the defects that the optical structure of the sensor in the prior art is too complex and the light fusion efficiency is low due to different optical path lengths, and to provide a new optical structure, which realizes the consistency of optical path lengths and light fusion through a compact cavity structure design.